The unknown voice actor sounds just like when June started doing Rocky back in the early 60's. Usually, when you recast a voice actor/actress (or for the sake of this site, Puppeteers) that have a unique rasp to their voice, they don't have that right sound. This time, I actually had to watch the commercial multiple times to realize there was a barely noticeable difference in voice quality. Other than the fact as, like I said, it sounds younger.
The short, however, supposedly features June, but only as Rocky with an unknown as Natasha, as well as other unknowns as Boris and Fearless Leader.
That said, I really hope the Peabody and Sherman movie comes with a toy like Rise of the Guardians, Turbo, and Croods did. You can never have too many Bullwinkle collectibles.